The present invention relates to an intake manifold for an internal-combustion engine with spark ignition. More particularly, the present invention relates to an intake manifold for such an engine including a distributor body from which the intake pipes leading to the individual combustion chambers of the engine branch off in a sequence corresponding to the firing order of the engine.
An intake manifold of the above-described type is disclosed in French Pat. No. 1,475,880, issued Feb. 27, 1967. Such an intake manifold offers advantages regarding the supply of the individual combustion chambers of the engine with the same fuel and air mixture as concerns quantity and ratio, particularly in an engine of the flat type (opposed cylinder type). In such engines, in which the cylinders are arranged in two rows, the customary firing order is 1-2-3-4 (or in the reverse sequence, respectively) with the cylinders 1 and 2 as well as the cylinders 3 and 4 being arranged to be successive in each cylinder row in the same direction. If, therefore, the intake manifold is not constructed so that the intake pipes branch off from the distributor body in a sequence corresponding to the firing order, the intake pipes, or the cylinders of each cylinder row, find completely different flow and mixture distribution conditions during intake. The two cylinders of a cylinder row take in at a crank angle spacing of 180.degree., and until the first cylinder of the cylinder row in question takes in again, there is a pause corresponding to a crank angle of 540.degree..